Ornamental Fish Production and Management

5.1.4 Water hardness

It is nothing but the total soluble calcium and magnesium salts present in the water expressed as its calcium carbonate equivalent. The total hardness of water however, includes the sulphates and chlorides of calcium and magnesium. The total hardness is mainly used to classify waters into ‘hard water’ or ‘soft water’. Water with hardness of 100-300 ppm have been found to be optimal for the normal growth of majority of ornamental fish. Water with less than 12 ppm require liming for higher production of fish. Hard water is also known to influence feed intake and growth of cichlids such as angel, black zebra, firemouth, blue morph and auratus.